Hi there, I wish to take a long distance bus from hangzhou west bus station to tunxi, huangshan.

I'll be staying in this city for a few days and travelling with a family of 4, should I purchase the long distance bus tickets a few days before I take the bus? Or will buying the tickets just before I set off be alright?
By the way, I'm looking to buy tickets from the 11.20 - 11.50pm timing

Also, may i know the opening hours of the west bus station? I can't seem to find it, thanks!